The present applicant took particular note of the technology of managing a database using a transaction log, and proposed a data synchronization method based on a one-to-one master/slave system in Japanese Patent Application Publication No. 2006-293910, and subsequently proposed a data synchronization method based on a one-to-N (wherein N is a positive integer) master/slave system in PCT/JP2010/054311 (hereinafter referred to as the “Earlier Unpublished Application”).
Here, a transaction log refers to the technology of realizing high-speed operations while maintaining the permanence of changes by recording the history of changes made to the database in an area that is different from the recording area of the database.
In particular, Japanese Patent Application Publication No. 2006-293910 focused on realizing a replication system by using a transaction log, and, with the Earlier Unpublished Application, a slave node that received a search command from a client sends a request message to a master node, the slave node requests the master node to send a transaction log up to the latest version of the update of the master database when the slave node does not receive a return message from the master node within a predetermined time, the master node that received the foregoing request sends the requested transaction log to the slave node, and the slave node refers to the received log and updates its own replica database.